1. Field of the Invention
The present application relates to a lamp tube, and in particular to a light-emitting diode (LED) lamp tube.
2. Description of the Related Art
Currently, there are two types of light-emitting diode (LED) lamp tubes in common use: all-plastic tubes and aluminum-plastic tubes. The structural strength and the thermal performance of the aluminum-plastic tubes are better than the all-plastic tubes.
FIG. 1 is a sectional view of a conventional aluminum-plastic lamp tube 10. The lamp tube 10 includes a cover 10a made of plastic, a heat sink 10b made of aluminum, and a light bar including a substrate 10c, at least a light-emitting element 10d, such as an LED, and several conductive wires 10e. The substrate 10c of the light bar can be fastened on the heat sink 10b by thermal grease G, such that the heat from the light bar can be dissipated through the heat sink 10b. 
However, it should be noted that the traditional aluminum-plastic lamp tube 10 must comply with electrical safety standards. For example, a creepage distance D between the conductive wires 10e on the light bar and the heat sink 10b has to exceed a specific value. Thus, the dimensions of the substrate 10c may not be reduced owing to the limitation of the creepage distance D, so as to increase the production cost of the lamp tube 10. Furthermore, as shown in FIG. 1, the thickness D′ of the heat sink 10b is about half of the entire thickness of the lamp tube 10. As such, it may also cause insufficient light-mixing distance of the lamp tube 10 (i.e. the distance between the light-emitting element 10d and the cover 10a), such that more LEDs are required to improve the illumination thereof. Consequently, the price-competitiveness of the product is adversely affected. For the reasons described above, an aluminum-plastic lamp tube which can comply with electrical safety standards, low cost requirements, and provide great illumination is needed.